runtime/cgo: support Handle even when CGO_ENABLED=0

[eliasnaur]

Go version

go1.21.0

What operating system and processor architecture are you using (go env)?

Windows

What did you do?

Run the program

package main

import "runtime/cgo"

func main() {
	println(cgo.NewHandle(new(int)))
}

on Windows (GOOS=windows).

What did you expect to see?

No error.

What did you see instead?

runtime.cgo_yield: relocation target _cgo_yield not defined
_cgo_init: relocation target x_cgo_init not defined
_cgo_thread_start: relocation target x_cgo_thread_start not defined
_cgo_pthread_key_created: relocation target x_cgo_pthread_key_created not defined
_crosscall2_ptr: relocation target x_crosscall2_ptr not defined
_cgo_bindm: relocation target x_cgo_bindm not defined
_cgo_notify_runtime_init_done: relocation target x_cgo_notify_runtime_init_done not defined
_cgo_getstackbound: relocation target x_cgo_getstackbound not defined

This issue may be fixed by forcing CGO_ENABLED=1 when using cgo.NewHandle, but I think that's the short-sighted fix. cgo.Handle is also useful for storing context when using the syscall facility for calling native code.

[prattmic]

cc @golang/runtime

[prattmic]

I wonder if we should have an equivalent cgo.Handle in package syscall for use there? (Alas, the name syscall.Handle is already taken on Windows)

[cherrymui]

Just importing the runtime/cgo package causes the same failure, without using Handle.

package main

import _ "runtime/cgo"

func main() {}

If we want to fix this, we need to guard things in runtime/cgo that interacts with C with cgo build tag.